IAX2 prune realtime fix

IAX2 prune realtime fix

Now prune_users() and prune_peers() are called instead of reload_config() to prune all users/peers that are realtime.  These functions remove all users/peers with the rtfriend and delme flags set. iax2_prune_realtime() also lacked the code to properly delete a single friend.  For example. if iax2 prune realtime <friend> was called, only the peer instance would be removed. The user would still remain.

(closes issue #14479)
Reported by: mousepad99
Review: http://reviewboard.digium.com/r/176/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@178838 65c4cc65-6c06-0410-ace0-fbb531ad65f3